The central aim of this program is to elucidate the genetic control of developing mammalian systems and the relationship between normal control and stem cell conversion to neoplasia. The mouse genes in which we are interested exemplify a hierarchy in the developmental progression. Their roles can best be examined in several different developing systems. The earliest events involve a set of alkaline phosphatase genes which will be isolated and characterized. These genes are especially active in early embryo stem cells, primordial germ cells, and early tumor stem cells and may be a prerequisite for stem cell maintenance. Proto-oncogenes, whose function in normal cells in unknown, may be involved in events in more specialized stem cells. Some of those associated with hematopoietic malignancy, e.g., c-myc, will be introduced into early hematopoietic stem cells by infection with retroviral vectors containing blood lineage-specific enhancers, to obtain expression and observe effects in the various cell lineages, after substituting the stem cells for those of host embryos. Farther along in the developmental hierarchy, unique products are expressed by specialized tissues, such as the crystallins in lens cells. To learn how specificity and timing are regulated from the stage of lens induction onward, we will introduce various constructs of recombinant crystallin genes into the mouse germ line, by injection into the zygote. In pigment cells, melanin production, involving tyrosinase, is specific but occurs relatively late. In order to detect the unpigmented precursor melanoblasts, to understand the color and pattern effects of certain mutant genes, and to observe early events in melanoma formation and invasion, the tyrosinase gene will be cloned and used as a probe. Constitutively expressed genes in mutant forms may cause other kinds of complex diseases for which there are no animal models. Models will be produced by selecting for HPRT-deficient cells and by screening for G-6-PD-deficient cells in a mutagenized population of a euploid and developmentally totipotent teratocarcinoma cell line. The cells, after injection into blastocysts, are capable of producing germ-line progeny which would provide the disease models for further study.